Kurt Hughes updated Trikala 19 trimaran

So Upchurchmr, we have an egg. it represents our hull shape. For a reverse bow the narrower end is up, the wide end down. This lets it slice through waves with them breaking over with minimal resistance. For a regular bow we turn the egg over (easy) and the narrow end is down with the wide end at deck level giving us progressively more buoyancy as each inch is immersed. It goes over the waves and is drier on deck. Now if we drop the egg it will have to be scrambled.

 

I think Locke Crowther knew how to get it right.
His International 23 Cat had the sliding tube system which worked very well.
It was fast , and though severely handicapped, was regularly placed in mixed racing at the
Sandringham yacht club in Melbourne in the late 1970s. It could be
(and was) pitchpoled when pushed downwind in gusty weather, under full main and spinnaker.
As a result I think the characteristics of the Buccaneer 24 should be carefully studied, because
it is reputed to have never been pitchpoled, which Samnz can attest to.

 

We so hope the non pitchpoled theory continue's into practise when we get ours out for sea trials os Locke sure knew a thing or two....

 

Doug,

You win.
I still don't think I got a useful answer.
But I don't care for any more useless answers.

Did you ever answer the required length of the bow to mast vs the mast to stern for a reverse bow setup to work? I asked that several times - just got A class this and A class this.

 

I think with Kurt it is a fad thing. He sure knows how to design boats that are great for the buck, and fast, but I don't see reverse bows on any boat that is not in some way constrained by some rule, or if DL says it all works with foils... For most boats people build for playing around in, racing on performance ratings, etc... Seems like a step backwards. Of course, it took me a while to get blunt bows when they first came out. Or to be precise, somewhere between the first and second ama built. But blunt bows, to my way of thiking, have virtually no downsides, I think the reverse bows have lot of potential downsides.

So far a couple of the first few boats I have seen from KHSD come out with these bows, seem like they don't mater at all. I don't see any advantage, other than cool factor. Also, timing is everything. And we know following what race these things hit design boards around the world on boats that had no business wearing them.

OK, So his site suggests we look here:

http://www.militaryphotos.net/forum...-Xbow-Sea-Axe-A-future-in-the-Military-Design

The video is very convincing, but it is not really analogous to our situation. I am not really even sure how analogous the X and flare bow boats are.

1) For any design there will be a sweet spot, so in comparisons the deal is to run a pure scientific test that compares your product at it's design sweet spot, to another working outside its sweet spot.

2) A motor boat is not a sail boat.

3) The X bow boat in the vid seems to be a lot higher freeboard that the flared bow.

also, is looks like it is sealed, so that essentially a total stuff will not sink a boat. But that requires a lot more complex build, which is great if you can go there, and save fuel and run better, but it does not really answer the question of whether this bow is better in all regards than a flared bow built to that tech level and at that cost. One could have a flared bow that was very similar to the X boat, only really differing in being flared, as opposed to being also a pig.

4) the X bow in this vid has two regions, a wave penetrating level, and then a much higher level that controls, spray, waves that are multiples of the baseline height etc... On the multi sailboats, or efficient motorboats, etc... we are probably never going to see that kind of scale. We are going to penetrate the wave, and then it is going to go pretty much wherever it wants to, all over the deck and crew.

5) Kurt mentions that the main advantages are that it is lighter, less windage, and less wave pitching. The later could be true, the first two would not inspire me to affect a working deck, for the marginal benefits.

He does have a rowboat design were the factors he mentions would seem to be well met by an X bow. But that boat has a lot of different design features. The bow it way over the heads of the crew, there is no deck to walk on, it is presumably being raced in some sense, in open water and weight and air drag will be critical in this use.

 

As far as comparing Kurt's beams to that other boat, if the intended cut is that he copied, well... Not that boat anyway. He has been flogging that beam design for decades. I always thought it was a bit of a joke, but as usual, when I updated my plans from the wayback machine, with a new set, it had the slidy beams, and the drawings are pretty convincing. There are details and they look like they would work.

That said, on my 24 you ain't getting it to trailering width with that set-up, and that is key to having a trailer sailer, this is what Kurt normally, and appropriately refers to as the slip option. Of course if the designed boat is small enough, then the slip option becomes a trailer sailer.

 

And probably worth every penny. Kurt will teach you how to build a boat, through his plans. Particularly given 2 below, it is money well spent. Dollars wise, I figure on 4+ dollars a pound for wood, and there is probably some similar number for composite, but there are so many degrees of cost you can throw at a composite boat, you know simple foam through to buying 800 dollar software to predict where the goo from your resin infusion set-up will end up...


2. How long would it take a ham fisted idiot to build one?

Don't build a boat, unless your main reason for doing so is because you want to build a boat; And having graduated from a 12 step program designed to eliminate that need you still can't stop yourself.

Roughly speaking the amas will each be one unit each; then if you build it next the main hull will be one unit; the beams are one unit; building or adapting it to a trailer is one unit; rigging it is one unit; Painting it could be one unit if you like it to look nice. Sourcing materials is one unit; Mental obsessing, is a lot of units; Blogging and documenting, no limit. Then multiply by 3.

It is impossible to put actual numbers on this stuff. Workspace is a possible doubler if one is comparing indoors to outdoors. Skill at making stuff, is probably a doubler, and another doubler for an expert at this kind of building. Boat building is fun and not that hard, but there is a huge range of ability out there, and motivation.

I had an ama fail when I built my KHSD, as a result of epoxy failure. So I built 3 amas. The 3rd was built after the rest of the project. It took 6 weeks part time to build the first, and 4 days part time to build the third. So by the time you are ready to quit, you will be pretty efficient.

 

Thanks ThomD!
I shall start saving my pocket money.
Cheers,
Adam

 

The egg wasn't that rotten.....It shows how the fullness is there to extend the bow low in the hull. The alternative is the grafted on bulbous bow of merchant ships.

 

Cavalier,
No the alternative is to extend the bow like Crowther did (or move the mast aft depending on your perspective).
By the way, like the C-class has (along with making it reversed).
My question boiled down to - did you have to extend the bow in order to allow yourself to incorporate the reversed bow?

No the egg wasn't that rotten, I just got hard boiled when I wanted an omelet.

 

So which sort of bow does this boat have? any guesses?

see here

http://www.catsailingnews.com/2012_10_01_archive.html

Richard Woods

 

The one I saw was very narrow, a requirement of the standard beam sliding system. Sliding beams might work on small boats but on bigger ones you have to have two people pulling very carefully to open it out (think how often you have pulled a drawer out of a chest and jammed it because it twisted. Then scale that up)

Richard Woods of Woods Designs

www.sailingcatamarans.com

 

Speaking of bows pitchpoling:

click:

 

yes but that one came upright again. Check out the video

Richard Woods

 

How about that!
http://www.youtube.com/watch?v=yqJ7YgN42Gg